1. Field of the Invention
The present invention relates to the general technical field of agricultural machinery. It relates more specifically to a seed drill including:
a hitching drawbar intended to be connected to a motor vehicle,
a body including
a chassis made up:
of a front chassis connected to said hitching drawbar, carrying opening tools and resting on the ground by means of wheels which are connected thereto in such a way as to be able to be moved heightwise by means of connecting elements, and
of a rear chassis connected to the front chassis by means of a central articulation the longitudinal axis of which is at least substantially vertical, and
a sowing device including, amongst other things, a hopper and elements for planting seeds in the ground, these elements being carried by the rear chassis.
2. Discussion of the Background
A seed drill such as this is known from the state of the art, particularly from patent application EP 0 612 464. In addition to the features listed above, this known seed drill also includes locking means installed between the front chassis and the rear chassis. During work, these locking means advantageously allow the rear chassis to pivot freely with respect to the front chassis about said central articulation. By contrast, during transport, these locking means eliminate said pivoting. With this known seed drill, the opening tools are intended to prepare lines for sowing, in which lines the planting elements deposit the seed. The free pivoting of the rear chassis about said central articulation makes it possible, very advantageously when said seed drill enters a bend, for example, for each planting element to remain in the sowing line prepared by the corresponding opening tool. Eliminating the pivoting of the rear chassis about said central articulation is, for its part, necessary to ensure that the seed drill is stable while it is being transported. To this end, said locking means include locking elements installed on the connecting elements connecting the wheels to said front chassis.
During the switch to the transport position, said wheels are moved away from said front chassis and the seed drill is raised off the ground. When the wheels are in the position furthest from the front chassis, said locking elements automatically come into contact against the stops connected to the rear chassis. This contact on one hand causes said rear chassis to align with respect to said front chassis and on another hand causes said central articulation to be locked. During the switch to the work position, the wheels are brought closer to the front chassis and the seed drill is lowered toward the ground. As soon as the wheels have left their position furthest from the front chassis, the locking elements automatically release the rear chassis. The latter can then once again pivot freely about the central articulation.
With this known seed drill, said central articulation is therefore unlocked, during the switch to the work position, before said planting elements have come into contact with the ground. In addition, during the switch to the transport position, said front and rear chassis are aligned and said central articulation is locked well after said planting elements have left the earth.
Under certain working conditions, this known seed drill may exhibit a drawback. What happens is that when the seed drill is inclined, the rear chassis naturally tends, because of its weight, to pivot with respect to the front chassis about said central articulation. Thus, during the switch to the transport position, with said seed drill being inclined, said rear chassis pivots about said central articulation as soon as said planting elements have come out of the earth. This then results in a shock, the violence of which varies according to the magnitude of the inclination, between said front chassis and said rear chassis. This repeated shock causes mechanical stresses which are detrimental to the life of the seed drill as a whole.
It is a purpose of the present invention to overcome this drawback of the state of the art.
Accordingly, the seed drill according to the present invention is one which includes means making it possible, as soon as said planting elements leave the earth, to align said rear chassis with respect to said front chassis. Thus, the shock described above is eliminated.
According to another feature of the invention, said alignment means also make it possible, during transport, to eliminate the pivoting of the rear chassis about the central articulation. The seed drill according to the invention therefore does not need additional locking means in order to ensure that the machine is stable during transport.
According to an additional feature of the invention, said alignment means also, during work, allow the rear chassis to pivot freely about the central articulation. The planting elements can therefore advantageously, when the seed drill according to the invention enters a bend, for example, follow the sowing lines prepared by the opening tools.
According to an additional feature of the invention, said alignment means also make it possible, during work if necessary, to eliminate the pivoting of the rear chassis about the central articulation. Said planting elements will be able, remarkably, even when working on a sideways slope, to follow the sowing lines prepared by the opening tools.